The present invention relates to a monitoring system for transmitting, receiving and recording image taken by an imaging apparatus such as a monitoring camera through a network and more particularly to an image monitoring method and system for storing image desired to be preserved over a long time.
Image monitoring systems are heretofore installed in facilities such as hotels, buildings, convenience stores, financial agencies, dams or roads for the purpose of prevention of crime and accident.
In the image monitoring system, a scene in a place to be monitored is taken by an imaging apparatus such as a camera and its image is transmitted to a monitoring center such as a superintendent's office or guardroom, so that the transmitted image is displayed on a monitoring screen to be monitored by a guard. Attention or warning is given according to the purpose of the system or as the need arises or the image data is recorded to be preserved. The image data contains voice and information accompanying the image (e.g. photographic place and time, photographer, information relative to the copyright or the right of portrait and conditions such as price) in addition to the image.
Recently, in the field of such a system, a network type image monitoring system is spreading in which the image taken by the imaging apparatus is digitized and transmitted through an IP (Internet Protocol) network represented by the Internet to thereby make monitoring.
At present, the network type image monitoring system of the main current is to deliver live image from an image transmission apparatus connected to an imaging apparatus such as a monitoring camera to an image receiving apparatus through a network and fits the monitoring form in which a monitoring person permanently stationed watches the live image at all times and copes with occurrence of a problem in accordance with conditions.
On the other hand, in the field of monitoring an image, there is another monitoring form in which the monitored image is recorded in addition to monitoring of the live image as described above and the recorded image is watched while retraced to the past when any problem occurs. The customer's need for such a record type monitoring form mainly exists in financial agencies and stores.
The network type image monitoring system includes an image storing and delivering server which can cope with the need for such a record type monitoring form.
Referring now to FIG. 2, an example of the network type image monitoring system including the image storing and delivering server is described. FIG. 2 schematically illustrates the conventional network type image monitoring system.
Numeral 101 denotes a network medium, 102 an image producing apparatus, 103 an image transmitting apparatus, 104 an image receiving apparatus, 105 an image display apparatus, 106 an image storing and delivering server and 107 a recording medium.
In FIG. 2, the network medium 101 is, for example, network cable, radio LAN (Local Area Network), public network or the like and has the function of transmitting data. Further, the network medium includes network apparatuses such as routers and hubs.
The image transmitting apparatus 103, the image receiving apparatus 104 and the storing and delivering server 106 are connected to the network medium 101 so that they can communicate with each other.
The image producing apparatus 102 includes, for example, an image pick-up unit such as a camera, which converts light into electricity to produce image.
The image transmitting apparatus 103 is constituted by, for example, an encoder apparatus including an interface for receiving image data from the image producing apparatus 102, an image codec and an network interface and converts input image data from the image production apparatus 102 into a form suitable for network transmission to be transmitted to the network medium 101. For example, when the input image from the image producing apparatus 102 is analog image, the image transmitting apparatus converts the analog image into digital image and compresses the digital image in accordance with the transmission band of the network medium 101 if necessary.
The image producing apparatus 102 and the image transmitting apparatus 103 may be a form combined into one apparatus.
The image receiving apparatus 104 is constituted by, for example, a decoder apparatus including an network interface, an image codec and an interface for outputting the image to at least one image display apparatus 105 and receives image data transmitted through the network medium 101 and converts the image data into a form that can be displayed by the image display apparatus 105 to be outputted to the image display apparatus 105. For example, when the image display apparatus 105 is a television monitor, analog conversion is made. Further, when the received image data is compressed image data, the image codec is used to expand the compressed image data.
The image display apparatus 105 displays the inputted image. The image display apparatus 105 includes, for example, a projecting device such as a television monitor, a CRT (Cathode-Ray Tube) of a computer or a liquid crystal monitor and converts electricity into light to be displayed as image.
The image receiving apparatus 104 and the image display apparatus 105 may be a form combined into one apparatus. It may include, for example, a form included in a television monitor, a form of a computer connected to a CRT or a form of a portable terminal such as a portable telephone equipped with a display device.
Further, the image receiving apparatus 104 also includes an operation interface for instructing the storing and delivering server 106 to make reproduction, fast-forwarding and the like. This interface may be, for example, a GUI (Graphical User Interface) displayed on a computer screen or a control panel terminal connected to the image receiving apparatus 104.
The storing and delivering server 106 is constituted by, for example, a personal computer (PC) including a network interface and an interface to the recording medium and has the function of receiving image data transmitted from the image transmitting apparatus 103 through the network medium 101 and recording the image data in the recording medium 107 connected thereto and the function of obtaining requested image data from the recording medium 107 in response to an image delivery request from the image receiving apparatus 104 and delivering the requested image data to the image receiving apparatus 104 through the network medium 101.
Further, the storing and delivering server 106 includes reproduction software stored therein. The image receiving apparatus 104 can receive the reproduction software in the download manner and can reproduce the image data delivered from the storing and delivering server 106.
The recording medium 107 is a medium such as, for example, a hard disk or a disk array for recording image data and is connected to the storing and delivering server 106 through a dedicated interface such as, for example, SCSI (Small Computer System Interface), ATA (AT Attachment) or FC (Fibre Channel) or an interface using an IP network such as SAN (Storage Area Network) or NAS (Network Attached Storage).
In FIG. 2, the image producing apparatus 102, the image transmitting apparatus 103, the image receiving apparatus 104 and the image display apparatus 105 are expressed by ones, although each of these apparatuses may be connected to the storing and delivering server 106 in the plural manner.
The storing and delivering server 106 can receive a plurality of different image data transmitted from a plurality of image transmitting apparatuses 103 simultaneously and record them. Further, in parallel therewith, the storing and delivering server 106 can deliver the plurality of different image data to a plurality of image receiving apparatuses 104 simultaneously. A unit in case where a series of image transmitted from an image transmitting apparatus is treated is named channel.
The physical capacity of the recording medium 107 connected to the storing and delivering server 106 is limited. The recording medium 107 is usually full in capacity in the course of time with difference in days depending on the size of image to be recorded or the frequency of recording when data is recorded therein continuously. Each time the recording medium is full, it is necessary to stop recording of data in the recording medium 107 in order to exchange the recording medium 107 or erase the recording medium 107 once and reuse it.
Such stop leads to a fatal problem in the case of the system in which monitoring and recording are made at all times (24 hours throughout the year) or when the time that recording is stopped is coincident with the time that the monitoring and recording are required.
In order to overcome the above problem, the storing and delivering server 106 adopts a so-called circulative recording system in which a virtual recording medium is constructed in the recording medium 107 by means of software and image is continued to be overwritten on old image automatically when the recording medium is full in capacity, so that nonstop operation is realized irrespective of the physical capacity of the recording medium 107.
Further, the storing and delivering server 106 is designed to have high performance and high reliability so that all objects to be recorded are recorded without error since the objects to be recorded are live image which disappears in a moment. Accordingly, the recording medium 107 is also often constructed into array configuration to have high performance and high reliability. The array configuration means the recording medium configuration such as, for example, RAID, having the redundancy.